What are the Three Plates that Make up the Mendocino Triple Junction?

The Mendocino Triple Junction is located in the Pacific Ocean near Cape Mendocino in northern California. This area is the most seismically active active regions of the San Andreas transform system [1]. Seismologists have measured over 80 earthquakes each year since 1983 that are magnitude 3.0 or greater. This seismic activity is due to the plate motions between the three plates of the lithosphere that form the Mendocino Triple Junction.

What is a Triple Junction?

A triple junction is the intersection of three plate boundaries. Plates are either ridges (R), trenches (T), or transform faults (F).

The Three Plates of the Mendocino Triple Junction

The concentration of earthquakes at Cape Mendocino is known as the Mendocino Triple Junction. This junction is where the Gorda plate (a south section of the Juan de Fuca Plate), the North American plate, and the Pacific plate meet.

This map shows the triple junction (red arrow) off the coast of Oregon in the United States.

Download GIS tectonic plates and boundaries data

The GIS tectonic plates and boundaries data used to create the map showing the three plates that form the Mendocino Triple Junction was downloaded from Github and is a conversion of the dataset originally published in the paper An updated digital model of plate boundaries by Peter Bird (Geochemistry Geophysics Geosystems, 4(3), 1027, doi:10.1029/2001GC000252, 2003).

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The Look of Maps: An Examination of Cartographic Design is a cartographic classic by Arthur H. Robinson originally published in 1952. The book was based on Robinson’s doctoral research “which investigated the relationship between science and art in cartography and the resultant refinement of graphic techniques in mapmaking to present dynamic geographic information.”